165. Hounsfield units thresholds are associated with major intraoperative blood loss and implant complications within 90 days of adult spinal deformity surgery

Abstract

<h3>BACKGROUND CONTEXT</h3> Several studies have suggested that Hounsfield units (HU) in the spine are associated with increased complications for adult spinal deformity (ASD) patients. <h3>PURPOSE</h3> The aim of this study is to assess whether there exists a threshold for HU that is associated with increased blood loss following ASD surgery. We hypothesize that HU below thresholds on spinal CT are predictive of increased blood loss during surgery and implant complications within 90 days after surgery for ASD. <h3>STUDY DESIGN/SETTING</h3> Retrospective analysis. <h3>PATIENT SAMPLE</h3> ASD patients who had HU measured in the spine were identified from a multicenter database. <h3>OUTCOME MEASURES</h3> High Intraoperative blood loss and implant complications within 90 days of surgery. <h3>METHODS</h3> HU at L1, upper instrumented vertebrae (UIV) and total averages were assessed. Threshold linear regression with Bayesian information criteria was utilized to identify optimal cut-offs for predicting high blood loss (>2100mL, top 25% by volume) or any implant complications within 90 days. Implant complications included loosening, breakage and dislocation of rods or screws. Multivariable logistic regression was utilized controlling for age, gender, comorbidity, osteotomy and levels fused. <h3>RESULTS</h3> Of 527 patients included, the mean age was 61±14. Mean L1 HU was 154.59±87, UIV HU was 175.1±304, and total average HU was 165±168. There were 59 patients with high blood loss (mean 5,026±233ml) and 467 with low blood loss (1,331±39.5ml). Threshold regression analysis identified that a cut-off of=140.33 was optimal for predicting high blood loss and=99.75 total average HU was optimal for predicting implant complications within 90 days of surgery. On multivariable analysis, L1 HU less than 140 was associated with 1.57x higher odds of high blood loss (P=0.032). Total average HU less than 100 was associated with a 3.6x higher odds of having an implant related failure within 90 days of surgery (P=0.035). <h3>CONCLUSIONS</h3> In this prospective multi-center study, Those with L1 HU=140 had a 1.52x higher odds of high blood loss. Patients with an average HUof=100 have 3.6x higher odds of implant related complication within 90 days of surgery. <h3>FDA DEVICE/DRUG STATUS</h3> This abstract does not discuss or include any applicable devices or drugs.